Since antibiotics and other antimicrobial drugs first became widely used in the World War II era, they have saved countless lives and blunted serious complications of many feared diseases and infections. The success of antimicrobials against disease-causing microbes is among modern medicine's great achievements. After more than 50 years of widespread use, however, many antimicrobials are not as effective as they used to be.
Over time, some bacteria have developed ways to circumvent the effects of antibiotics. Widespread use of antibiotics is thought to have spurred evolutionarily adaptations that enable bacteria to survive these powerful drugs. Other microbes such as viruses, fungi, and parasites have developed resistance as well. Antimicrobial resistance provides a survival benefit to microbes and makes it harder to eliminate infections from the body. Ultimately, the increasing difficulty in fighting off microbes leads to an increased risk of acquiring infections in a hospital or other setting.
Diseases such as tuberculosis, gonorrhea, malaria, and childhood ear infections are now more difficult to treat than they were just a few decades ago. Drug resistance is an especially difficult problem for hospitals harboring critically ill patients who are less able to fight off infections without the help of antibiotics. Heavy use of antibiotics in these patients selects for changes in bacteria that bring about drug resistance. Unfortunately, this worsens the problem by producing bacteria with greater ability to survive even in the presence of our strongest antibiotics. These even stronger drug-resistant bacteria continue to prey on vulnerable hospital patients.
According to CDC statistics:                * Nearly 2 million patients in the United States get an infection in the hospital each year;        * About 90,000 of those patients die each year as a result of their infection, up from 13,300 patient deaths in 1992;        * More than 70 percent of the bacteria that cause hospital-acquired infections are resistant to at least one of the antibiotics most commonly used to treat them; and        * People infected with antibiotic-resistant organisms are more likely to have longer hospital stays and require treatment with second- or third-choice medicines that may be less effective, more toxic, and more expensive.        
In short, antimicrobial resistance is driving up health care costs, increasing the severity of disease, and increasing the death rates from certain infections. Therefore, there is a long-felt need in the art for new antimicrobial therapies and particularly therapies that target alternative mechanisms of action.
The need to develop new antimicrobials, as well as new potential drug targets, is especially acute in the case of P. aeruginosa infections in CF patients, where the natural antibiotic resistance of the organism and the ability to form biofilms (bacteria encapsulated in a polymeric matrix) accounts for significant mortality in such patients1-3. The inhibitors of the present invention provide a new class of antimicrobial agents to target infections that are persistently difficult to combat with the current spectrum of antimicrobial agents. P. aeruginosa is one example of a bacteria that is resistant to many antibiotics and has acquired resistance to others and is classified as having broad spectrum resistance. Most recently reports on the epidemiology of bactermia in early bone marrow transplant patients indicated numerous multi-drug resistant (MDR) gram negative strains, defined as an isolate with resistance to at least two of the following: third- or fourth-generation cephalosporins, carbapenems or piperacillin-tazobactam. Of 411 transplant recipients fever occurred in 333, and 91 developed bacteremia (118 isolates): 47% owing to Gram-positive, 37% owing to Gram-negative, and 16% caused by Gram-positive and Gram-negative bacteria. Pseudomonas aeruginosa (22%), Klebsiella pneumoniae (19%) and Escherichia coli (17%) accounted for the majority of Gram-negative isolates, and 37% were MDR4.
The final step in heme utilization and iron acquisition in many pathogens is the oxidative cleavage of heme by heme oxygenase (HO), yielding iron, biliverdin and carbon monoxide. The present invention is based on iron being an essential requirement and HO being a therapeutic target for antimicrobial drug development.